Numerical simulation of transient flow field in a mixed-flow pump during starting period

Wei, Li; Zhang, Yang; Shi, Weidong; Ji, Leilei; Yang, Yongfei; Ping, Yuanfeng

doi:10.1108/hff-06-2017-0220

Cited by 34 publications

(18 citation statements)

References 14 publications

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“…Literatures and our former researches concluded that, in spite its time-averaging simplification, the standard k-ɛ can provide a good result for the flow field in different types of pumps. 1,2,27 As a result, the standard k-ɛ model based on the Reynolds averaged Navier–Stokes equation is selected, as it offers a good compromise between computational effort and numerical accuracy. Steady simulations for different flow rates 0.2 Q des , 0.4 Q des , 0.6 Q des , 0.8 Q des , and 1.0 Q des are calculated for 1500 iterations at first, which is followed by the transient simulation using the steady field as the initial condition.…”

Section: Methodsmentioning

confidence: 99%

“…The mixed-flow pump is widely used in agricultural irri- gation, thermal power plant, and chemical process systems, as it collects advantages of both centrifugal and axial flow pumps. 1,2 The head-flow characteristic of mixed-flow pumps is often required to keep in a small incline, which usually gives rise to unstable flow in the pump especially under part-loading discharge. 3 Recent researches in turbomachines reveal that the so called positive-slope characteristic on the head-flow curve is mainly caused by rotating stalls in the impellers or guide vanes.…”

Section: Introductionmentioning

confidence: 99%

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Numerical investigation on the unstable flow at off-design condition in a mixed-flow pump

Yang

Wei

Shi

et al. 2019

Proceedings of the Institution of Mechanical Engineers, Part A:

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The mixed-flow pump is wildly used in industrial and agricultural fields, and the requirements for its stability become more and more restricted with the improvement of the capacities. When the pump is operated under part-loading conditions, unstable characteristic like rotating stall happens and brings intensive vibration and noise. To reveal the internal unstable flow characteristics in mixed-flow pump, unsteady numerical simulation is conducted under different flow rates in the current research. The secondary flow and the vortex induced by the unsteady flow in the pump, which vary with the change of the flow rate, are analyzed according to the simulation results. Pressure fluctuation in different parts of the impeller is numerically predicted and correlated to the rotating stall propagation process. With the reduction of the flow discharge, a critical flow rate (0.6 Qdes in the current model pump) is found related to the rotating stall inception. Unstable vortex structure is found in part of the flow passages of the impeller under the stall inception stage; 0.56 Qdes is the flow rate related to the deep rotating stall under which stable stall vortexes are found in each flow passage of the impeller. Three types of pressure fluctuation characteristics representing different flow field pattern in the impeller are found. When the pump is working at designed flow rate, the pressure fluctuation is regular with the dominant frequency being the rotation frequency fs of the rotor. At the stall inception condition, when the stall core appears in the flow passages of the impeller in turn, the amplitude of the pressure fluctuation is increased and the dominant frequency is changed to a low-frequency signal. When the flow rate is reduced below deep stall condition, owning to the reflux from the guide vane and the intensive rotor–stator interaction, the blade passing frequency of the guide vane fb2 becomes the dominant frequency. Finally, unsteady characteristics of the flow field under stall inception condition are analyzed to demonstrate the propagation process of the rotating stall. The stall vortex is found to propagate from the stalled flow passage to the next, through the tip area of the blade leading edge. During the propagation process, the first vortex shrinks and disappears gradually, while the second vortex grows continuously, and the third vortex shows up at the vanishment of the first stall vortex. This research provides detailed information for the unstable flow especially related to rotating stall evolution with the variation of the operating flow rate of the mixed-flow pump with guide vane.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Numerical investigation on the unstable flow at off-design condition in a mixed-flow pump

Yang

Wei

Shi

et al. 2019

Proceedings of the Institution of Mechanical Engineers, Part A:

Self Cite

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show abstract

“…Mixed-flow pump is a kind of industrial and agricultural pump, which could be widely used in irrigation, mine engineering, power stations and water supply [1][2][3][4]. It can meet the requirements of low head and high flow when operating at different situations.…”

Section: Literature Reviewmentioning

confidence: 99%

Research of transient rotor–stator interaction effect in a mixed-flow pump under part-load conditions

Cao

Wei

et al. 2019

J Braz. Soc. Mech. Sci. Eng.

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In order to analyze the unsteady flow characteristic and the pressure fluctuation features of mixed-flow pump caused by the interaction between the impeller and guide vanes under part-load conditions, the unsteady flow field in the mixed-flow pump was numerically simulated based on the standard k-ε turbulence model. The pressure distribution and the velocity distribution in the rotor-stator interaction (RSI) zones were acquired, and the time domain and frequency domain of the pressure fluctuation were emphatically analyzed. The results showed that the velocity within the rotor-stator interaction zones is mainly affected by the relative position of impeller and guide vane. With the decrease in flow rate condition, the flow fields become more violent and more vortexes generate in the RSI zone, which causes much energy losses. With the rotation of impeller, the vortexes generating from RSI zones move into the guide vane and dissipate in the guide vane passage in the end. The pressure pulsations at various monitoring points fluctuate periodically, and there appear four peak and four trough values with the same number of leaves. The dominant frequency of pressure pulsation was approximate to the impeller blade passing frequency (BPF). Within the rotor-stator interaction zones, the pressure pulsation coefficient in the rotor-stator interaction zone of the mixed-flow pump changes most obviously. The BPF and double and triple frequency of the pressure pulsation are dominant frequencies, and the frequency distribution range is relatively concentrated.

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“…e transient behavior of the pump was analyzed using pump characteristic curves [16]. Li et al [17] found that in the startup process of the mixed-flow pump, the flow stabilized in the impeller, the scale of vortex decreased gradually as the rotating speed approached the rated speed, and the transient effect disappeared.…”

Section: Introductionmentioning

confidence: 99%

Transient Characteristics of Water-Jet Propulsion with a Screw Mixed Pump during the Startup Process

Han

Zhang

et al. 2020

Mathematical Problems in Engineering

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In order to investigate the transient hydrodynamic characteristics of water-jet propulsion with a screw mixed pump during the startup period and to overcome the difficulties in measuring the transient process parameters over a very short period of time, a method based on a flume experiment combined with computational fluid dynamics (CFD) is proposed. The thrust and torque of the pump-jet propulsion according to mooring status at different rotational speeds were measured by the test, which provided a group of data for the boundary and initial conditions of the numerical calculation of the user-defined function (UDF). Consecutive changes in the parameters of the water-jet propulsion dynamics can be captured from the numerical simulation of the startup process with the UDF. Thus, the transient hydrodynamic characteristics of water-jet propulsion according to time or rotation speed were obtained. The results show that the relationship between the thrust or torque of the water-jet propeller and pump rotational speed is close to the quadratic functions. The energy characteristic parameters of screw mixed water-jet pump, such as the flow rate, head, shaft power, and efficiency, rapidly increase and decrease and then remain relatively stable.

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Numerical simulation of transient flow field in a mixed-flow pump during starting period

Cited by 34 publications

References 14 publications

Numerical investigation on the unstable flow at off-design condition in a mixed-flow pump

Numerical investigation on the unstable flow at off-design condition in a mixed-flow pump

Research of transient rotor–stator interaction effect in a mixed-flow pump under part-load conditions

Transient Characteristics of Water-Jet Propulsion with a Screw Mixed Pump during the Startup Process

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